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Organometallics 2007, 26, 3138-3148
Mercury-Free Preparation, Characterization, and Molecular Structure of Tricyanovinylferrocene Using an Unusual Reaction between Ferrocene and Tetracyanoethylene Victor N. Nemykin,* Alexander Y. Maximov, and Alexey Y. Koposov Department of Chemistry & Biochemistry, UniVersity of Minnesota Duluth, Duluth, Minnesota 55812 ReceiVed February 21, 2007
A direct reaction between ferrocene (FcH) and tetracyanoethylene (TCNE) in various solvents and within a wide range of temperatures has been investigated in order to optimize the preparation of tricyanovinylferrocene. Under optimized reaction conditions, tricyanovinylferrocene was prepared in ∼26% yield along with cyanoferrocene as a major reaction product in the reaction between 1 equiv of FcH and 2 equiv of TCNE for 10 min in sulfolane at 110 °C. It was proposed that the reaction proceeds via a single-electron-transfer step, which results in the formation of a spectroscopically detected [FcH]•+[TCNE]•intermediate followed by homolytic cleavage of the C-CN bond. The possible phase transition in tricyanovinylferrocene has been tested by X-ray crystallography at 173 and 293 K. The prominent visible band observed in the UV-vis spectrum of tricyanovinylferrocene has been unambiguously assigned to a metal-to-ligand charge-transfer transition on the basis of experimental and theoretical (TDDFT) data, while its solvatochromic behavior was tested using the Kamlet-Taft model. It has been found that the solvatochromism observed in tricyanovinylferrocene predominantly depends on the value of dipolarity/ polarizability parameter π* in the Kamlet-Taft equation. The significant anisotropy of the quadrupole doublet in the Mo¨ssbauer spectra of tricyanovinylferrocene and cyanoferrocene was explained on the basis of DFT calculations. Introduction Ferrocene-containing porphyrins and phthalocyanines have been intensively investigated during the last few decades primarily because of their potential applications in switchable molecular optical and electronic nanodevices.1 Recently, we have shown that the magnesium complex of 2(3),7(8),12(13),17(18)-tetracyano-3(2),8(7),13(12),18(17)-tetraferrocenyl-5,10,15,20-tetraazaporphyrin has unusual optical properties in the near-IR region, which can be useful for practical applications in optical limiting devices.2 This tetraazaporphyrin was prepared by template tetramerization of the so far poorly characterized tricyanovinylferrocene (1), the common synthesis of which requires the use of a highly toxic chloromercurioferrocene precursor.2,3 In order to avoid the use of costly or highly toxic reagents for the preparation of 1, we examined in detail the direct tricyanovinylation reaction between ferrocene and tetracyanoethylene in variety of solvents and under different reaction conditions and have found a simple way for the preparation of 1 in large quantities and high purity. In addition, spectroscopic properties, molecular structure, and solvatochromism of complex * Author to whom correspondence should be addressed. E-mail:
[email protected]. (1) Schmidt, E. S.; Calderwood, T. S.; Bruice, T. C. Inorg. Chem. 1986, 25, 3718. Uosaki, K.; Kondo, T.; Zhang, X. Q.; Yanagida, M. J. Am. Chem. Soc. 1997, 119, 8367. Boyed, P. D.; Burrell, A. K.; Campbell, W. M.; Cocks, P. A.; Gordon, K. C.; Jameson, G. B.; Officer, D. L.; Zhao, Z. Chem. Commun. 1999, 637. Baumann, T. F.; Nasir, M. S.; Sibert, J. W.; White, A. J. P.; Olmstead, M. M.; Williams, D. J.; Barrett, A. G. M.; Hoffman, B. M. J. Am. Chem. Soc. 1996, 118, 10479. Jin, Z.; Nolan, K.; McArthur, C. R.; Lever, A. B. P.; Leznoff, C. C. J. Organomet. Chem. 1994, 468, 205. Poon, K.-W.; Yan, Y.; Li, X.; Ng, D. K. P. Organometallics 1999, 18, 3528. (2) Nemykin, V. N.; Kobayashi, N. Chem. Commun. 2001, 165. (3) Perevalova, E. G.; Lemenovskii, D. A.; Alekseev, V. P.; Grandberg, K. I.; Nesmeyanov, A. N. IzV. Acad. Nauk SSSR, Ser. Khim. 1972, 8, 1867.
1 were carefully investigated by various experimental and theoretical approaches.
Experimental Section Preparation of Compounds. The synthesis of ferrocenylcontaining complexes was carried out in an oxygen-free dry argon atmosphere using dry degassed solvents. Ferrocene and tetracyanoethylene were purchased from TCI and used without further purification. Solvents were purchased either from Aldrich Chemical Co. or Acros Chemical Co. and purified by distillation as follows: acetonitrile from CaH2, followed by Li2CO3-KMnO4, and finally from P2O5; CH2Cl2, CHCl3, and butyronitrile from CaH2; toluene from sodium-benzophenone; ethanol from sodium ethoxide; sulfolane, DMF, and DMSO by distillation over molecular sieves (4 Å) under reduced pressure. Silica gel (60 Å, 70-230 mesh) was purchased from Sorbent Technologies. Synthesis of Tricyanovinylferrocene (1) and Cyanoferrocene (2). Method A. A 1.28 g (10 mmol) portion of tetracyanoethylene was added to a preheated (100 °C) solution of 0.93 g (5 mmol) of ferrocene in 10 mL of sulfolane. Immediately after addition, the color of the solution changed first to green and later to blue. The reaction mixture was heated continually with stirring for 10 min, and then, it was cooled to room temperature. The resulting solution was poured into 50 mL of water, and the obtained precipitate was filtered and washed several times with water. The resulting dark brown-black powder was dissolved in CH2Cl2, filtered, and purified by column chromatography on silica gel using 4:1 toluene/hexane as an eluent. The first, yellow band contains unreacted ferrocene as confirmed by 1H and 13C NMR spectra. The second, orange band consists of pure cyanoferrocene 2, while the third, dark blue band is the target compound 1. All three products were collected and the solvent was evaporated, yielding ferrocene (102 mg, 11%), cyanoferrocene 2 (390 mg, 37%), and tricyanovinylferrocene 1 (120 mg, 8.4%), respectively. Complex 1: mp 130-131 °C (hexane,
10.1021/om070160k CCC: $37.00 © 2007 American Chemical Society Publication on Web 05/19/2007
Mercury-Free Preparation of TricyanoVinylferrocene
Organometallics, Vol. 26, No. 13, 2007 3139
Table 1. Optimization of Experimental Conditions for Preparation of Complex 1
a
entry
solvent
T (°C)
t (min)
FcH (mmol)
TCNE (mmol)
purification methoda
yield of 1 (%)
1 2 3 4 5 6 7 8 9 10 11 12 13
sulfolane sulfolane sulfolane sulfolane sulfolane sulfolane sulfolane sulfolane sulfolane DMF DMSO acetonitrile butyronitrile
150 130 120 120 120 110 100 100 100 110 110 reflux reflux
10 10 10 10 10 10 10 5 10 10 10 180 30
5 5 5 5 5 5 5 10 10 5 5 5 5
5 5 5 7.5 10 10 10 20 20 10 10 10 10
A A A A A A A B B B B C C
